Eutrophic river and lake water treatment system and treatment method

Abstract

The invention belongs to the technical field of sewage treatment, and provides a eutrophic river and lake water body treatment system and method, the system comprises a phosphorus removal unit, an oxygen elimination unit and a nitrogen removal unit; the nitrogen removal unit is an autotrophic denitrification nitrogen removal unit; the oxygen elimination unit is arranged at the front end of the denitrification unit and is used for reducing dissolved oxygen in the water body and then discharging the water body into the denitrification unit for autotrophic denitrification nitrogen removal treatment. The method comprises the following steps: extracting a to-be-treated river and lake water body, and carrying out magnetic coagulation dephosphorization treatment to obtain a dephosphorized water body; carrying out oxygen elimination treatment on the dephosphorized water body to reduce dissolved oxygen of the dephosphorized water body so as to obtain a low-oxygen water body; the low-oxygen water body is fed into a denitrification unit to be subjected to autotrophic denitrification nitrogen removal treatment, and a denitrified water body is obtained; reoxygenation treatment is conducted on the denitrified water body, and then the water body is discharged back to rivers and lakes. The system and the method do not need to add an organic carbon source, have the advantages of low treatment cost, simple operation, high efficiency and small equipment size, are suitable for bypass treatment of river and lake water bodies, ensure the quality of treated water, and can effectively remove total nitrogen, total phosphorus and SS in the water bodies.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and specifically relates to a eutrophic river and lake water treatment system and a treatment method. Background Art

[0002] Nitrogen and phosphorus pollutants are the main causes of eutrophication of water bodies and are important control indicators for water bodies. Usually, when the total phosphorus and total nitrogen in water exceed a certain value, there is a risk of eutrophication. Under suitable temperature and other conditions, it may lead to the rapid reproduction of algae and other plankton, causing the dissolved oxygen in the water to decrease and the water quality to deteriorate. At present, the sources of nitrogen and phosphorus in water mainly include: non-point source pollution caused by the use of pesticides and fertilizers in agricultural activities and livestock and poultry farming, centralized discharge from municipal and industrial sewage treatment facilities, overflow sewage from the combination of rainwater and sewage into the drainage system during rainfall, and the release of endogenous nitrogen and phosphorus in sediments in lakes and slow-flowing water bodies. In recent years, with the implementation of a series of policies and regulations, the treatment level and emission standards of my country's sewage treatment facilities have been significantly improved, and the nitrogen and phosphorus discharged into environmental water bodies by existing sewage treatment plants are strictly controlled. However, agricultural non-point source pollution, overflow sewage and nitrogen and phosphorus pollution caused by endogenous release still significantly affect the water quality of rivers and lakes, especially in some villages and towns that do not have sound sewage collection and treatment facilities. Due to unreasonable sewage discharge and agricultural non-point source pollution, the total nitrogen content in some rivers can even be as high as 5~10 mg / L, and the total phosphorus concentration can reach more than 0.3 mg / L. The water body has seriously deteriorated, greatly affecting the living environment and bringing potential health risks. Therefore, this type of water body needs to be purified.

[0003] At present, the treatment and control technologies for nitrogen and phosphorus pollutants in river and lake water bodies mainly include bypass treatment and in-situ treatment. Among them, bypass treatment technology is to extract or introduce polluted water into an artificial branch, and discharge the pollutants back to the original water body after reducing them through external treatment devices and artificial wetlands, ecological ditches, facilities and building components with filter beds or contact reaction functions set up on the branch. In-situ treatment mainly uses biological floating islands placed in the water body, suspended fillers and combined ecological restoration technologies to reduce nitrogen and phosphorus.

[0004] However, existing denitrification treatment technologies have great limitations. For example, in-situ treatment technologies such as biological floating islands and suspended filler combination ecological restoration technologies have been widely used and are more suitable for treating water bodies and continuously improving water environment quality. However, due to their low treatment load, such technologies are more suitable for water bodies with low eutrophication risks. They have limited removal rates for polluted water bodies with high concentrations, and take several days to several months to take effect. At the same time, it is difficult to meet the treatment requirements when facing the impact load caused by overflow sewage and non-point source pollution during the flood season.

[0005] The extraction bypass treatment technology has a stronger processing capacity than the in-situ ecological treatment technology, but in order to achieve the ideal deep phosphorus and nitrogen removal effect, artificial wetlands, ecological ditches, facilities and building components with filter beds or contact reaction functions require a longer reaction time and a larger area. At the same time, the phosphorus removal materials loaded in artificial wetlands are mostly based on the principles of adsorption and surface chemical precipitation. After long-term use, problems such as adsorption saturation and reaction interface saturation are prone to occur, which affects the treatment effect and increases the work of replacing filter materials.

[0006] There are reports in the prior art on the use of biological denitrification technology for denitrification of river and lake water bodies, but the current use of biological denitrification technology in the treatment of river and lake water bodies is relatively limited. For example, the use of heterotrophic microorganisms for denitrification requires an external carbon source, which is costly; the use of autotrophic microorganisms for denitrification has a great impact on the activity of microorganisms due to the water quality, making it difficult to carry out denitrification treatment in a sustained and effective manner; and the existing biological denitrification technology is affected by water quality fluctuations, etc., and the degree of denitrification is limited, so it is difficult to promote and apply. Summary of the invention

[0007] In view of the deficiencies in the above-mentioned prior art, the present invention aims to provide a eutrophic river and lake water treatment system and method. The system and method do not require the addition of an organic carbon source, have low treatment costs, are simple and efficient to operate, have a small equipment size, are suitable for bypass treatment of river and lake water bodies, have guaranteed water quality, and can effectively remove total nitrogen, total phosphorus and SS in the water body.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A eutrophic river and lake water treatment system, comprising a phosphorus removal unit, an oxygen removal unit and a nitrogen removal unit; The denitrification unit is an autotrophic denitrification unit; The oxygen removal unit is arranged at the front end of the denitrification unit, and is used to reduce the dissolved oxygen in the water body and then discharge it into the denitrification unit for autotrophic denitrification treatment.

[0009] In one embodiment of the present application, the phosphorus removal unit is arranged before the oxygen removal unit; The phosphorus removal unit includes a coagulation section, a flocculation section and a magnetic separation section which are arranged in sequence, and also includes a phosphorus removal agent dosing device, a magnetic medium dosing device, a coagulant dosing device and a magnetic medium recovery device; the phosphorus removal agent dosing device and the magnetic medium dosing device are connected to the coagulation section, and the phosphorus removal agent and the magnetic medium are added to the coagulation section; the coagulant dosing device is connected to the flocculation section, and the coagulant is added to the flocculation section; the magnetic medium recovery device is connected to the magnetic separation section and the coagulation section, and the flocs captured by the magnetic separation section are separated by magnetic media and recovered and added to the coagulation section.

[0010] In one embodiment of the present application, the oxygen removal unit is one of the following: It comprises a pipeline mixing deoxidizer and a first deoxidizer dosing device, wherein the pipeline mixing deoxidizer is arranged before the water inlet of the denitrification unit, and the first deoxidizer dosing device is arranged to add a first deoxidizer to the pipeline mixing deoxidizer, so that the water body is deoxidized in the pipeline mixing deoxidizer; It comprises a chemical deoxidation tank and a second deoxidation agent dosing device, wherein the chemical deoxidation tank is arranged before the water inlet of the denitrification unit, and the second deoxidation agent dosing device is arranged to add a second deoxidation agent to the chemical deoxidation tank, so that the water body can be deoxidized in the chemical deoxidation tank; It comprises a vacuum container and a vacuum pumping device. The vacuum container is arranged before the water inlet of the denitrification unit. The vacuum pumping device can vacuum the vacuum container to achieve oxygen removal of the water in the vacuum container.

[0011] In one embodiment of the present application, the autotrophic denitrification unit is configured as one of the forms of an autotrophic denitrification filter tank, a contact reaction tank, an artificial wetland, an ecological ditch or a structure.

[0012] In one embodiment of the present application, the autotrophic denitrification unit is configured as an autotrophic denitrification filter tank, including an autotrophic denitrification filter tank, a backwashing device, and a soluble electron donor dosing device.

[0013] In one embodiment of the present application, a reoxygenation unit is further included. The reoxygenation unit is arranged after the water outlet of the denitrification unit and before being discharged back to the river or lake water body, and is used to increase the dissolved oxygen in the water body.

[0014] In one embodiment of the present application, the reoxygenation unit includes a combination of one or more of a waterfall tank, a stirring tank, a hydraulic mixer, and an aeration device.

[0015] A method for treating eutrophic river and lake water, using the eutrophic river and lake water treatment system as described in any one of the above, comprises the following steps: S1, extracting river and lake water to be treated for magnetic coagulation and phosphorus removal to obtain phosphorus-removed water; S2, deoxygenating the dephosphorization water to reduce the dissolved oxygen in the dephosphorization water to obtain a hypoxic water body; S3, sending the hypoxic water body to a denitrification unit for autotrophic denitrification treatment to obtain a denitrified water body; S4, reoxygenating the denitrified water and then discharging it back into rivers and lakes.

[0016] In one embodiment of the present application, in step S1, extracting river and lake water to be treated for magnetic coagulation and phosphorus removal treatment to obtain phosphorus-removed water, specifically comprising: The water from rivers and lakes to be treated is extracted and mixed with a dephosphorizing agent and a magnetic medium for reaction, and then a coagulant is added for flocculation. After flocculation, magnetic medium flocs are separated to obtain dephosphorized water and magnetic medium flocs. After the magnetic medium flocs are broken up and separated, the magnetic medium is recycled; and / or, In step S2, the dephosphorization water body is subjected to deoxygenation treatment to reduce the dissolved oxygen in the dephosphorization water body to obtain a hypoxic water body, which specifically includes one of the following treatment methods: The dephosphorization water is mixed with a first deoxidizer through a pipeline mixing deoxidizer to perform deoxidation treatment, and the dissolution of the dephosphorization water is reduced to below 1 mg / L to obtain a hypoxic water body; The dephosphorization water body is subjected to deoxygenation reaction with a second deoxidizer in a chemical deoxidation tank, and the dissolution of the dephosphorization water body is reduced to below 1 mg / L to obtain a hypoxic water body; The dephosphorization water body is subjected to deoxygenation treatment in a vacuum container under vacuum conditions to reduce the dissolution of the dephosphorization water body to below 1 mg / L, thereby obtaining a hypoxic water body; and / or, In step S3, the hypoxic water body is sent to a denitrification unit for autotrophic denitrification treatment to obtain a denitrified water body, which specifically includes: Passing the hypoxic water body into an autotrophic denitrification filter tank, and performing autotrophic denitrification treatment through contact filtration of a denitrification carrier filler layer to obtain a denitrified water body; and / or, In step S4, the denitrified water body is reoxygenated and then discharged back into the river or lake water body, which specifically includes: The denitrified water body is reoxygenated by waterfall, stirring, hydraulic mixing or aeration to restore the dissolved oxygen of the denitrified water body to 6-8 mg / L, and then discharged back into the river and lake water body.

[0017] In one embodiment of the present application, the processing method further satisfies one or more of the following conditions: The phosphorus removal agent includes one or more combinations of PAC, PAFC, PFC, PFS, PFCS, PAFCS, PFAS, and polyferrous iron; The coagulant aid includes one or a combination of PAM and diatomaceous earth; The total phosphorus concentration of the dephosphorization water body is lower than 0.1 mg / L, and the SS concentration is lower than 10 mg / L; The first deoxidizer includes one or a combination of sodium sulfite and sodium thiosulfate, and the dosage is 23-90 mg / L based on the volume of the dephosphorization water body; or, the second deoxidizer includes one or a combination of sodium sulfite and sodium thiosulfate, and the dosage is 23-90 mg / L based on the volume of the dephosphorization water body; or, the second deoxidizer is ferrous sulfate, and the dosage is 6-30 mg / L based on the volume of the dephosphorization water body; During the vacuum deoxidation treatment, the relative vacuum degree in the vacuum container is controlled to be -0.05~-0.09MPa; During the vacuum deoxidation treatment, the dephosphorization water body stays in the vacuum container for 5 to 40 minutes; The denitrification water body has a total nitrogen concentration lower than 1.5 mg / L, a nitrate nitrogen concentration lower than 1.0 mg / L, a SS concentration lower than 5 mg / L, and a turbidity lower than 1 NTU.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. The eutrophic river and lake water treatment system and treatment method of the present invention are provided with a phosphorus removal unit and a nitrogen removal unit for phosphorus removal and nitrogen removal treatment respectively, and an autotrophic denitrification technology is adopted to denitrify by autotrophic denitrification and denitrification microorganisms, and an oxygen removal unit is provided at the front end of the denitrification unit (autotrophic denitrification and denitrification unit) to deoxygenate the water body, which can effectively solve the problem of oxygen enrichment in natural river and lake water bodies, avoid the inhibition of oxygen-rich water bodies on the denitrification activity of the autotrophic denitrification and denitrification unit, ensure that the autotrophic denitrification unit effectively denitrifies the water body, and the low dissolved oxygen water body can further promote the efficiency of autotrophic denitrification and denitrification, and improve the treatment effect. The system and method do not require additional addition of organic carbon sources, have low operating costs (the operating costs of heterotrophic denitrification are reduced by more than 50%, and there is no risk of COD exceeding the standard), simple equipment, small footprint, simple and efficient operation, suitable for bypass treatment of river and lake water bodies, guaranteed water quality, and can effectively remove total nitrogen, total phosphorus and SS (suspended solids) in the water body.

[0019] 2. The phosphorus removal unit adopts magnetic coagulation treatment to remove phosphorus, which can effectively remove total phosphorus and SS in river and lake water bodies. It has strong phosphorus removal capacity and is suitable for the treatment of large-scale river and lake water bodies with large water quality fluctuations. It is easy to control and has low treatment cost. The phosphorus removal unit is set before the oxygen removal unit and the autotrophic denitrification denitrification unit to solve the problem that magnetic coagulation treatment cannot effectively remove nitrogen. At the same time, when the treatment load is high, if some flocs cannot be effectively captured, they can be further filtered and purified by the subsequent autotrophic denitrification denitrification unit to ensure the removal efficiency of total phosphorus and SS and the quality of the effluent.

[0020] 3. Before discharging the water back into rivers and lakes, the treated water is reoxygenated through a reoxygenation unit to increase and control the dissolved oxygen in the returned water, which can effectively reduce the impact on the returned water in rivers and lakes.

[0021] 4. The eutrophic river and lake water treatment system and treatment method of the present invention have simple equipment, small footprint, easy control, low operating cost, and little impact from water quality and quantity fluctuations. It can effectively remove total nitrogen, total phosphorus and SS in river and lake water, and the treated water quality is guaranteed. It realizes the application of autotrophic denitrification technology in the field of river and lake water treatment, has strong applicability, and is easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 It is a schematic diagram of the process structure of the eutrophic river and lake water treatment system of the present invention.

[0024] Figure 2 The present invention is a flow chart of the method for treating eutrophic river and lake water bodies. DETAILED DESCRIPTION

[0025] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0026] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0027] The embodiment of the present invention provides a eutrophic river and lake water treatment system and treatment method, such as Figure 1 As shown, the eutrophic river and lake water treatment system is a bypass treatment system for river and lake water, including a phosphorus removal unit, an oxygen removal unit and a nitrogen removal unit.

[0028] Among them, the denitrification unit is an autotrophic denitrification unit, which uses autotrophic denitrification microorganisms to achieve denitrification of water bodies.

[0029] The oxygen removal unit is arranged at the front end of the denitrification unit to reduce the dissolved oxygen in the water body, so that the dissolved oxygen concentration of the water body is reduced and then discharged into the denitrification unit for autotrophic denitrification treatment.

[0030] The water bodies of natural rivers and lakes are often in an oxygen-rich state, and their dissolved oxygen can be close to saturation. Setting up an oxygen removal unit at the front end of the denitrification unit can effectively solve the inhibitory effect of the oxygen-rich characteristics of natural river and lake water bodies on autotrophic denitrification microorganisms. At the same time, the dissolved oxygen content of the water body after oxygen removal is low, which can help autotrophic denitrification microorganisms to efficiently exert their denitrification effect. Therefore, the limiting difficulties of the application of raw denitrification technology in the treatment of natural river and lake water bodies are solved. The use of autotrophic denitrification denitrification technology does not require the addition of organic carbon sources, is simple to operate, and has low costs; in conjunction with the phosphorus removal unit, it can effectively solve the problem of nitrogen and phosphorus pollution in natural eutrophic river and lake water bodies.

[0031] Preferably, the phosphorus removal unit is arranged before the oxygen removal unit, that is, the denitrification unit is located after the phosphorus removal unit.

[0032] The phosphorus removal unit comprises a coagulation part, a flocculation part and a magnetic separation part which are arranged in sequence, and also comprises a phosphorus removal agent dosing device, a magnetic medium dosing device, a coagulant aid dosing device and a magnetic medium recovery device.

[0033] The phosphorus removal agent dosing device and the magnetic medium dosing device are connected to the coagulation section, and are used to automatically dosing the phosphorus removal agent and the magnetic medium to the coagulation section, respectively. The coagulant dosing device is connected to the flocculation section, and is used to dosing the coagulant to the flocculation section. The magnetic medium recovery device is configured to connect the magnetic separation section and the coagulation section, and separate and recover the flocs containing phosphorus and magnetic medium captured by the magnetic separation section by magnetic medium, and the recovered magnetic medium is added to the coagulation section for recycling.

[0034] Specifically, the river and lake water to be treated enters the coagulation section, and the dephosphorization agent dosing device and the magnetic medium dosing device respectively add the dephosphorization agent and the magnetic medium, and the dephosphorization agent and the magnetic medium react with the phosphate pollutants in the river and lake water to form flocs; then it enters the flocculation section, reacts with the coagulant added by the coagulant dosing device, and forms larger phosphorus-containing and magnetic medium flocs that are easier to capture; then it enters the magnetic separation section, and the flocs are captured by magnetic separation equipment (such as magnetic disks, magnetic drums, etc.), and the captured phosphorus-containing and magnetic medium flocs enter the magnetic medium recovery device to separate the magnetic medium from the flocs. The separated magnetic medium can be recovered and added to the coagulation section for recycling, and the separated phosphorus-containing sludge is discharged, thereby realizing the phosphorus removal treatment of the river and lake water.

[0035] In one embodiment, the deoxidation unit includes a pipeline mixing deoxidizer and a first deoxidizer dosing device. The pipeline mixing deoxidizer is arranged on the pipeline before the water inlet of the denitrification unit; the first deoxidizer dosing device is connected to the pipeline mixing deoxidizer and is arranged to automatically add the first deoxidizer to the pipeline mixing deoxidizer, so that the water body is mixed with the first deoxidizer in the pipeline deoxidizer to react and chemically deoxidize, thereby obtaining a water body with low dissolved oxygen.

[0036] Specifically, the water discharged from the phosphorus removal unit enters the pipeline mixing deoxidizer, and at the same time, the first deoxidizer dosing device dissolves the first deoxidizer (such as sodium sulfite, sodium thiosulfate, etc.) and adds it to the pipeline mixing deoxidizer. The water and the first deoxidizer are fully mixed hydraulically in the pipeline mixing deoxidizer to achieve a deoxidation reaction, and the deoxidized water enters the subsequent denitrification unit.

[0037] In another embodiment, the deoxidation unit includes a chemical deoxidation tank and a second deoxidant dosing device. The chemical deoxidation tank is arranged before the water inlet of the denitrification unit, that is, between the water outlet of the magnetic separation part of the dephosphorization unit and the water inlet of the denitrification unit; the second deoxidant dosing device is connected to the chemical deoxidation tank and is arranged to add the second deoxidant to the chemical deoxidation tank, so that the water body is mixed with the second deoxidant in the chemical deoxidation tank to react and achieve chemical deoxidation, thereby obtaining a water body with low dissolved oxygen.

[0038] Specifically, the water discharged from the phosphorus removal unit enters the chemical deoxidation tank, and the second deoxidant (such as sodium sulfite, sodium thiosulfate, ferrous sulfide, etc.) is added to the chemical deoxidation tank through the second deoxidant dosing device. The water is mixed with the second deoxidant in the chemical deoxidation tank to achieve deoxidation, and the deoxidized water enters the subsequent denitrification unit.

[0039] In the third embodiment, the deoxidation unit includes a vacuum container and a vacuum pump. The vacuum container, such as a vacuum deoxidizer, is arranged before the water inlet of the denitrification unit, that is, the vacuum container is arranged between the magnetic separation part of the dephosphorization unit and the denitrification unit; the vacuum pump (such as a vacuum pump) is connected to the vacuum container, and can evacuate the vacuum container to achieve deoxidation of the water in the vacuum container. When this vacuum deoxidation method is adopted, an inlet valve / inlet pump is also provided at the water inlet end of the vacuum container to introduce the water into the vacuum container; at the same time, a water outlet pump is also provided between the vacuum container and the denitrification unit to draw out the water in the vacuum container and discharge it to the denitrification unit.

[0040] Specifically, during operation, the vacuum device is first turned on, and the vacuum degree is designed according to the concentration of dissolved oxygen to be removed. Preferably, the relative vacuum degree is set to -0.05MPa~-0.09MPa. When the relative vacuum degree in the vacuum container reaches the set value, the water inlet valve / water inlet pump is turned on to introduce the water outlet of the dephosphorization unit into the vacuum container, and the liquid level and relative vacuum degree in the vacuum container are ensured to be within the set range. Under the vacuum environment, the gas including oxygen dissolved in the water body will be released, thereby reducing the concentration of dissolved oxygen in the water; preferably, the residence time of the dephosphorization water body in the vacuum container is controlled to be more than 5 minutes, and more preferably controlled to be within 5~40 minutes. After deoxygenation, the water body is discharged to the subsequent denitrification unit through the water outlet pump for denitrification treatment.

[0041] The autotrophic denitrification denitrification unit (denitrification unit) can be set up as one of the forms of an autotrophic denitrification filter tank, a contact reaction tank, an artificial wetland, an ecological ditch or a structure, all of which are denitrification reactions carried out by autotrophic denitrifying microorganisms under anoxic or anaerobic conditions.

[0042] The autotrophic denitrification and denitrification unit is preferably configured as an autotrophic denitrification filter tank, which includes an autotrophic denitrification filter tank, a backwashing device, and a soluble electron donor dosing device. A denitrification carrier filler layer is provided in the autotrophic denitrification filter tank, and the autotrophic denitrification microorganisms are attached to the surface of the denitrification carrier. During operation, the effluent of the deoxygenation unit enters the autotrophic denitrification filter tank, flows from top to bottom through the denitrification carrier filler layer, and under the action of the autotrophic denitrification microorganisms, the nitrate nitrogen in the water body is reduced to nitrogen gas, thereby achieving the removal of total nitrogen in the water body. It is preferred to control the residence time of the water body in the autotrophic denitrification filter tank to be 20 to 60 minutes.

[0043] After the autotrophic denitrification filter has been running for a period of time, the filter packing layer needs to be backwashed. A backwashing device is set up to automatically backwash the autotrophic denitrification filter. A soluble electron donor dosing device is set up to automatically dosing soluble electron donors to the autotrophic denitrification filter to better cope with water quality fluctuations and ensure the quality of the effluent.

[0044] Further preferably, the eutrophic river and lake water treatment system also includes a reoxygenation unit, which is arranged after the water outlet of the denitrification unit and before being discharged back to the river and lake water body, and is used to increase the dissolved oxygen concentration of the discharged water body.

[0045] The reoxygenation unit may include a combination of one or more of a waterfall pool, a stirring pool, a hydraulic mixer, and an aeration device. The dissolved oxygen in the effluent water body is increased by dropping from a height, stirring, hydraulic mixing, aeration, etc., so as to reduce the impact on the water body of rivers and lakes and reduce the risk of eutrophication.

[0046] The treatment system also includes a screen filter unit, a lifting pump, etc., which are arranged before the phosphorus removal unit to perform coarse filtration on river and lake water, remove coarse impurities in the water, and lift the filtered river and lake water to the coagulation part of the phosphorus removal unit for treatment reaction.

[0047] The eutrophic river and lake water treatment system also includes a control unit, which is connected to the phosphorus removal unit, the oxygen removal unit, the nitrogen removal unit and the reoxygenation unit to achieve automated coordinated control of the system.

[0048] Based on the same invention purpose and concept, the present invention also provides a method for treating eutrophic river and lake water bodies, which is suitable for bypass denitrification and phosphorus removal treatment of natural eutrophic river and lake water bodies.

[0049] like Figure 1 and Figure 2 As shown, the eutrophic river and lake water treatment method adopts the above-mentioned eutrophic river and lake water treatment system for treatment, and includes the following steps: S1, extracting water from rivers and lakes to be treated for magnetic coagulation and phosphorus removal to obtain phosphorus-removed water.

[0050] Specifically, water from rivers and lakes to be treated is drawn into the coagulation section for mixed reaction with the dephosphorization agent and the magnetic medium, so that the phosphate pollutants in the water from rivers and lakes react to form chemical flocs; then the water is introduced into the flocculation section for reaction with the added coagulant aid to form larger phosphorus-containing and magnetic medium flocs that are easier to capture; the flocculated water enters the magnetic separation section, where the magnetic medium flocs are captured by magnetic separation equipment (such as magnetic disks and magnetic drums) to obtain dephosphorized water and magnetic medium flocs; the captured phosphorus-containing and magnetic medium flocs enter the magnetic medium recovery device for separation and recovery of the magnetic medium and flocs.

[0051] Among them, the phosphorus removal agent may include one or more combinations of PAC (polyaluminum chloride), PAFC (polyaluminum ferric chloride), PFC (polyferric chloride), PFS (polyferric sulfate), PFCS (polyferric chloride sulfate), PAFCS (polyaluminum ferric sulfate), PFAS (polyaluminum sulfate), and polyferrous iron.

[0052] The coagulant aid includes one or a combination of PAM (polyacrylamide), diatomaceous earth.

[0053] Preferably, the total phosphorus concentration in the phosphorus removal water body after treatment in step S1 is controlled to be below 0.1 mg / L, and the SS (suspended solids) concentration is below 10 mg / L, which can effectively ensure that the water body that meets the discharge requirements is obtained after subsequent treatment.

[0054] S2, deoxygenating the dephosphorization water obtained in step S1 to reduce the dissolved oxygen concentration of the dephosphorization water and obtain hypoxic water.

[0055] Specifically, the deoxygenation treatment can be any of the following three treatment methods: (i) Chemical deoxidation is adopted, by setting a pipeline mixing deoxidizer on the pipeline, and setting a first deoxidizer dosing device to automatically add the first deoxidizer to the mixing deoxidizer. The dephosphorization water body is drained through the pipeline mixing deoxidizer, and is fully mixed with the first deoxidizer in the pipeline mixing deoxidizer to deoxidize and obtain hypoxic water body. Preferably, the dissolved oxygen concentration of the hypoxic water body is controlled to be less than 1 mg / L.

[0056] The first deoxidizer can be one of sodium sulfite and sodium thiosulfate or a combination of the two. The first deoxidizer is dissolved and then added continuously. Based on the volume of the dephosphorization water body, the dosage of the first deoxidizer is preferably controlled to be 23-90 mg / L.

[0057] (ii) Chemical deoxidation is adopted, a chemical deoxidation tank is set between the phosphorus removal unit and the denitrification unit, and a second deoxidation agent dosing device is provided to automatically dosing the second deoxidation agent into the chemical deoxidation tank. During operation, the dephosphorization water is introduced into the chemical deoxidation tank, and mixed / contacted with the second deoxidation agent added by the second deoxidation agent dosing device to achieve deoxidation and obtain hypoxic water. It is preferred to control the dissolved oxygen concentration of the hypoxic water to be less than 1 mg / L.

[0058] The second oxygen scavenger can be sodium sulfite, sodium thiosulfate or ferrous sulfate.

[0059] When the second deoxidizer is sodium sulfite, sodium thiosulfate or a combination of the two, the second deoxidizer is dissolved and added continuously or batchwise, preferably in an amount of 23-90 mg / L based on the volume of the dephosphorization water.

[0060] When the second deoxidizing agent is ferrous sulfide, a fixed reaction zone is set in the chemical deoxidizing tank, the ferrous sulfide particles / powder are added to the fixed reaction zone, and the dephosphorization water is introduced into the fixed reaction zone to contact with the ferrous sulfide for deoxidation reaction; the ferrous sulfide is added in a batch manner, and the addition frequency can be controlled to be once every 1 to 15 days. Preferably, the addition amount of the ferrous sulfide is controlled to be 6 to 30 mg / L based on the volume of the dephosphorization water.

[0061] (III) Using vacuum deoxidation, a vacuum container (such as a vacuum deoxidizer) is set between the phosphorus removal unit and the nitrogen removal unit, and a vacuum device (such as a vacuum pump) is provided to evacuate the vacuum container. During operation, the vacuum container is first evacuated to the set vacuum range, and then the dephosphorization water is introduced into the vacuum container, and the liquid level and vacuum are maintained within the set range. The water is kept under vacuum for 5 to 40 minutes for deoxidation to obtain hypoxic water. It is preferred to control the relative vacuum degree in the vacuum container to -0.05 to -0.09 MPa, so that hypoxic water with a dissolved oxygen concentration below 1 mg / L can be obtained.

[0062] Controlling the dissolved oxygen concentration in low-oxygen water bodies to below 1 mg / L can effectively ensure that the autotrophic denitrifying microorganisms in the subsequent autotrophic denitrification unit are in a suitable state, thereby ensuring efficient denitrification treatment.

[0063] S3, sending the hypoxic water body obtained after the oxygen removal treatment in step S2 to a denitrification unit, performing autotrophic denitrification treatment under the action of a denitrification carrier and autotrophic denitrifying microorganisms to obtain a denitrified water body.

[0064] Preferably, denitrification treatment is carried out in the form of an autotrophic denitrification filter, and the low-oxygen water body is passed into the autotrophic denitrification filter, passes through the denitrification carrier filler layer from top to bottom, contacts and reacts with the denitrification carrier and autotrophic denitrifying microorganisms in the filler layer, and is filtered through the filler layer to achieve denitrification treatment of the water body and obtain denitrified water.

[0065] It is preferred to control the reaction time of the hypoxic water in the autotrophic denitrification filter to 20-60 minutes and the filtration rate to 1-8 m / h.

[0066] The denitrified water obtained has a total nitrogen concentration lower than 1.5 mg / L, a nitrate nitrogen concentration lower than 1.0 mg / L, a total phosphorus concentration lower than 0.1 mg / L, a SS concentration lower than 5 mg / L, and a turbidity lower than 1 NTU.

[0067] S4, reoxygenating the denitrified water treated in step S3 to increase the dissolved oxygen concentration in the water, and then discharging it back into the natural river and lake water. Reoxygenating the treated water can effectively avoid the impact of hypoxic water on natural river and lake water, and reduce the risk of eutrophication.

[0068] Specifically, denitrified water bodies are reoxygenated by means of waterfalls (falling from a high place), stirring, hydraulic mixing or aeration, so that the dissolved oxygen in the deoxygenated water body is restored to 6-8 mg / L before being discharged back into natural rivers and lakes. This reoxygenation treatment method is simple and effective, and can improve the treatment effect of river and lake water bodies.

[0069] In summary, the eutrophic river and lake water treatment system and treatment method of the present invention are provided with a phosphorus removal unit and a nitrogen removal unit for phosphorus removal and nitrogen removal treatment respectively, and an autotrophic denitrification technology is adopted to perform nitrogen removal by autotrophic denitrification and denitrification microorganisms, and an oxygen removal unit is provided at the front end of the denitrification unit (autotrophic denitrification and denitrification unit) to perform oxygen removal treatment on the water body, which can effectively solve the problem of oxygen enrichment in natural river and lake water bodies, avoid the inhibition of the denitrification activity of the autotrophic denitrification and denitrification unit by the oxygen-rich water body, ensure that the autotrophic denitrification unit effectively denitrifies the water body, and the low dissolved oxygen water body can further promote the efficiency of autotrophic denitrification and denitrification, and improve the treatment effect. The system and method do not require additional addition of organic carbon sources, have low operating costs (the operating costs of heterotrophic denitrification are reduced by more than 50%, and there is no risk of COD exceeding the standard), simple equipment, small footprint, simple and efficient operation, and are suitable for bypass treatment of eutrophic river and lake water bodies. The quality of treated water is guaranteed, and total nitrogen, total phosphorus and SS (suspended solids) in the water body can be effectively removed.

[0070] The phosphorus removal unit adopts magnetic coagulation treatment to remove phosphorus, which can effectively remove total phosphorus and SS in river and lake water bodies. It has strong phosphorus removal capacity and is suitable for the treatment of large-scale river and lake water bodies with large water quality fluctuations. It is easy to control and has low treatment cost. The phosphorus removal unit is arranged before the oxygen removal unit and the autotrophic denitrification denitrification unit to solve the problem that magnetic coagulation treatment cannot effectively remove nitrogen. At the same time, when the treatment load is high, if some flocs cannot be effectively captured, they can be further filtered and purified by the subsequent autotrophic denitrification denitrification unit to ensure the removal efficiency of total phosphorus and SS and the quality of the effluent water.

[0071] Before discharging the water back into rivers and lakes, the treated water is reoxygenated through a reoxygenation unit to increase and control the dissolved oxygen in the returned water, which can effectively reduce the impact on the returned water in rivers and lakes and reduce the risk of eutrophication.

[0072] The eutrophic river and lake water treatment system and treatment method of the present invention have simple equipment, small footprint, easy control, low operating cost, and little impact from water quality and quantity fluctuations. It can effectively remove total nitrogen, total phosphorus and SS in river and lake water, and the quality of treated water is guaranteed. It realizes the application of autotrophic denitrification technology to large-scale treatment of river and lake water, has strong applicability, and is easy to promote and apply.

[0073] When the total nitrogen in the inlet water is 2~15mg / L, the total phosphorus is 0.1~1.0m / L, and the SS is 10~200mg / L, the treatment system and treatment method of the present application can be used to reduce the total nitrogen concentration in the effluent to below 1.5mg / L, the nitrate nitrogen concentration to below 1.0mg / L, the total phosphorus concentration to below 0.1mg / L, the SS concentration to below 5mg / L, and the turbidity to below 1NTU, thereby obtaining effluent that meets the treatment requirements.

Claims

1. A eutrophic river and lake water treatment system, characterized in that: It includes phosphorus removal unit, oxygen removal unit and nitrogen removal unit; The denitrification unit is an autotrophic denitrification unit; The oxygen removal unit is arranged at the front end of the denitrification unit, and is used to reduce the dissolved oxygen in the water body and then discharge it into the denitrification unit for autotrophic denitrification treatment.

2. The eutrophic river and lake water treatment system according to claim 1, characterized in that: The phosphorus removal unit is arranged before the oxygen removal unit; The phosphorus removal unit includes a coagulation section, a flocculation section and a magnetic separation section which are arranged in sequence, and also includes a phosphorus removal agent dosing device, a magnetic medium dosing device, a coagulant dosing device and a magnetic medium recovery device; the phosphorus removal agent dosing device and the magnetic medium dosing device are connected to the coagulation section, and the phosphorus removal agent and the magnetic medium are added to the coagulation section; the coagulant dosing device is connected to the flocculation section, and the coagulant is added to the flocculation section; the magnetic medium recovery device is connected to the magnetic separation section and the coagulation section, and the flocs captured by the magnetic separation section are separated by magnetic media and recovered and added to the coagulation section.

3. The eutrophic river and lake water treatment system according to claim 1, characterized in that: The oxygen removal unit is one of the following: It comprises a pipeline mixing deoxidizer and a first deoxidizer dosing device, wherein the pipeline mixing deoxidizer is arranged before the water inlet of the denitrification unit, and the first deoxidizer dosing device is arranged to add a first deoxidizer to the pipeline mixing deoxidizer, so that the water body is deoxidized in the pipeline mixing deoxidizer; It comprises a chemical deoxidation tank and a second deoxidation agent dosing device, wherein the chemical deoxidation tank is arranged before the water inlet of the denitrification unit, and the second deoxidation agent dosing device is arranged to add a second deoxidation agent to the chemical deoxidation tank, so that the water body can be deoxidized in the chemical deoxidation tank; It comprises a vacuum container and a vacuum pumping device. The vacuum container is arranged before the water inlet of the denitrification unit. The vacuum pumping device can vacuum the vacuum container to achieve oxygen removal of the water in the vacuum container.

4. The eutrophic river and lake water treatment system according to claim 1, characterized in that: The autotrophic denitrification unit is configured in the form of an autotrophic denitrification filter tank, a contact reaction tank, an artificial wetland, an ecological ditch or a structure.

5. The eutrophic river and lake water treatment system according to claim 4, characterized in that: The autotrophic denitrification and denitrification unit is arranged in the form of an autotrophic denitrification filter tank, comprising an autotrophic denitrification filter tank, a backwashing device and a soluble electron donor dosing device.

6. The eutrophic river and lake water treatment system according to claim 1, characterized in that: It also includes a reoxygenation unit, which is arranged after the water outlet of the denitrification unit and before it is discharged back to the river or lake water body, and is used to increase the dissolved oxygen in the water body.

7. The eutrophic river and lake water treatment system according to claim 6, characterized in that: The reoxygenation unit includes a combination of one or more of a waterfall tank, a stirring tank, a hydraulic mixer, and an aeration device.

8. A method for treating eutrophic river and lake water, characterized in that: The eutrophic river and lake water treatment system according to any one of claims 1 to 7 is used for treatment, comprising the following steps: S1, extracting river and lake water to be treated for magnetic coagulation and phosphorus removal to obtain phosphorus-removed water; S2, deoxygenating the dephosphorization water to reduce the dissolved oxygen in the dephosphorization water to obtain a hypoxic water body; S3, sending the hypoxic water body to a denitrification unit for autotrophic denitrification treatment to obtain a denitrified water body; S4, reoxygenating the denitrified water and then discharging it back into rivers and lakes.

9. The method for treating eutrophic river and lake water according to claim 8, characterized in that: In step S1, the water from rivers and lakes to be treated is extracted for magnetic coagulation and phosphorus removal treatment to obtain phosphorus-removed water, which specifically includes: The water from rivers and lakes to be treated is extracted and mixed with a dephosphorizing agent and a magnetic medium for reaction, and then a coagulant is added for flocculation. After flocculation, magnetic medium flocs are separated to obtain dephosphorized water and magnetic medium flocs. After the magnetic medium flocs are broken up and separated, the magnetic medium is recycled; and / or, In step S2, the dephosphorization water body is subjected to deoxygenation treatment to reduce the dissolved oxygen in the dephosphorization water body to obtain a hypoxic water body, which specifically includes one of the following treatment methods: The dephosphorization water is mixed with a first deoxidizer through a pipeline mixing deoxidizer to perform deoxidation treatment, and the dissolution of the dephosphorization water is reduced to below 1 mg / L to obtain a hypoxic water body; The dephosphorization water body is subjected to deoxygenation reaction with a second deoxidizer in a chemical deoxidation tank, and the dissolution of the dephosphorization water body is reduced to below 1 mg / L to obtain a hypoxic water body; The dephosphorization water body is subjected to deoxygenation treatment in a vacuum container under vacuum conditions to reduce the dissolution of the dephosphorization water body to below 1 mg / L, thereby obtaining a hypoxic water body; and / or, In step S3, the hypoxic water body is sent to a denitrification unit for autotrophic denitrification treatment to obtain a denitrified water body, which specifically includes: Passing the hypoxic water body into an autotrophic denitrification filter tank, and performing autotrophic denitrification treatment through contact filtration of a denitrification carrier filler layer to obtain a denitrified water body; and / or, In step S4, the denitrified water body is reoxygenated and then discharged back into the river or lake water body, which specifically includes: The denitrified water body is reoxygenated by waterfall, stirring, hydraulic mixing or aeration to restore the dissolved oxygen of the denitrified water body to 6-8 mg / L, and then discharged back into the river and lake water body.

10. The method for treating eutrophic river and lake water according to claim 9, characterized in that: The processing method also meets one or more of the following conditions: The phosphorus removal agent includes one or more combinations of PAC, PAFC, PFC, PFS, PFCS, PAFCS, PFAS, and polyferrous iron; The coagulant aid includes one or a combination of PAM and diatomaceous earth; The total phosphorus concentration of the dephosphorization water body is lower than 0.1 mg / L, and the SS concentration is lower than 10 mg / L; The first deoxidizer includes one or a combination of sodium sulfite and sodium thiosulfate, and the dosage is 23-90 mg / L based on the volume of the dephosphorization water body; or, the second deoxidizer includes one or a combination of sodium sulfite and sodium thiosulfate, and the dosage is 23-90 mg / L based on the volume of the dephosphorization water body; or, the second deoxidizer is ferrous sulfate, and the dosage is 6-30 mg / L based on the volume of the dephosphorization water body; During the vacuum deoxidation treatment, the relative vacuum degree in the vacuum container is controlled to be -0.05~-0.09MPa; During the vacuum deoxidation treatment, the dephosphorization water body stays in the vacuum container for 5 to 40 minutes; The denitrification water body has a total nitrogen concentration lower than 1.5 mg / L, a nitrate nitrogen concentration lower than 1.0 mg / L, a SS concentration lower than 5 mg / L, and a turbidity lower than 1 NTU.

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